Question

A nonconducting container filled with 25kg of water at 20C is
fitted with stirrer, which is made to turn by gravity acting on a
weight of mass 35kg. The weight falls slowly through a distance of
5m in driving the stirrer. Assuming that all work done on the
weight is transferred to the water and that the local acceleration
of gravity is 9.8m/s2, determine:
a) The amount of work done on the water.
b) The internal-energy change of the water.
c)The final temperature of the water, for which Cp =4.18
kJ/kgC.
d)The amount of heat that must be removed from the water to return
it to it initial temperature.
e) The total energy change of the universe because of (1) the
process of lowering the weight, (2) the process of cooling the
water back to its initial temperature, and (3) both processes
together.